Supplementary Material

GO showed a D band at 1336 cm-1 and G band at 1586 cm-1, respectively. After modification and reduction of GO, the intensity ratio of the D band and G band (ID/IG) increased significantly (Figure 2(c)). The Raman spectrum of G also contains a D bands at 1321 cm-1 and a G band at 1578 cm-1, however, with an increased D/G intensity ratio compared to that in GO. The 2D peak of the GO located at wavenumber of about 2652 cm-1 with a low intensity. By reduction of the GO, the peak of 2D band broadened along with a tail toward the higher wavenumbers.